1. Field of the Invention
The present invention is related to a printer and a printing method for recording an image on a lenticular sheet.
2. Description of the Related Arts
A technique for observing a stereo image with use of a lenticular sheet where a plurality of lenticular lenses in a shape of a semicircular are arranged in a lateral direction is known. For observing the stereo image, for example, one of whole images taken from two viewpoints in the lateral direction is sliced into linear images (stripes), and then the stripes are interlaced with stripes sliced from the other of the whole images. These are printed on the rear side of the lenticular sheet such that each stripe is printed on a corresponding lenticular lens. Accordingly, the stereo image can be observed since a left eye sees one of the whole images and a right eye sees the other whole image having parallax with the former one. In addition, a technique for observing a stereo image with an enhanced stereoscopic effect by use of N (N≧3) images from different viewpoints is also known. In this technique, each of N whole images is sliced into stripes, and these stripes are aligned on the lenticular lenses in sequential order.
As a method for positioning the linear images on the rear side of the lenticular sheet, there is a method that a print (hard copy) where all linear images are arranged and printed is attached on the rear side of the lenticular sheet. In addition, some printers utilize a method that the linear images are directly printed on the rear side of the lenticular sheet.
In case that the image is directly recorded on the rear side of the lenticular sheet, a position of the image must be correctly adjusted on a position of the lenticular lens (hereinafter called as the lens position). In addition, detection of a lens pitch is required in this case. For this purpose, some printers, for example printers of U.S. Pat. No. 7,543,910 (corresponding to Japanese Laid-open Patent Publication No. 2007-144974) and Japanese Laid-open Patent Publication No. 2007-127521, provide an optical sensor near a recording head for detecting a position of the lenticular lens during transportation in a main-scanning direction so that operation of the recording head is controlled (for example discharge timing of ink is controlled).
On the other hand, there are thermal printers which use a thermal head for recording an image. As the thermal printer, there are a heat-sensitive type in which a heater element array of the thermal head directly heats a thermosensitive recording sheet for coloring, a thermofusible type in which a rear side of an ink ribbon is heated so that ink on the ink ribbon is transferred, and a sublimation type in which an ink is sublimated for adhesion.
However, in case the thermal head is used for recording an image directly on the lenticular sheet, it is difficult that the optical sensor for detecting the lens pitch and so on is provided near the thermal head, since the thermal head has a high temperature in recording. In addition, since the thermal head presses a recording medium for recording and tension is occurred on the lenticular sheet from a part pressed by the thermal head, it is possible that the lens pitch is changed because the lenticular sheet is stretched by the tension. Accordingly, in some measurement positions, the lens pitch required for controlling a recording position of an image cannot be correctly measured. The printers of U.S. Pat. No. 7,543,910 (corresponding to Japanese Laid-open Patent Publication No. 2007-144974) and Japanese Laid-open Patent Publication No. 2007-127521 disclose no solution for these problems.